# Copyright 2016-2020 Christoph Reiter
# SPDX-License-Identifier: MIT

import os
import sys
import io
import json
import asyncio
import traceback
import hashlib
import functools
import gzip
import yaml
import datetime
from asyncio import Event
from urllib.parse import urlparse, quote_plus
from typing import Any, Dict, Tuple, List, Set, Optional
from email.utils import parsedate_to_datetime

import httpx
from aiolimiter import AsyncLimiter
import zstandard

from .appstate import state, Source, get_repositories, SrcInfoPackage, Package, DepType, Repository, BuildStatus, PkgMeta, \
    ExtInfo, ExtId
from .appconfig import CYGWIN_METADATA_URL, REQUEST_TIMEOUT, AUR_METADATA_URL, ARCH_REPO_CONFIG, PKGMETA_URLS, \
    SRCINFO_URLS, UPDATE_INTERVAL, BUILD_STATUS_URLS, UPDATE_MIN_RATE, UPDATE_MIN_INTERVAL
from .utils import version_is_newer_than, arch_version_to_msys, extract_upstream_version
from . import appconfig
from .exttarfile import ExtTarFile


def get_mtime_for_response(response: httpx.Response) -> Optional[datetime.datetime]:
    last_modified = response.headers.get("last-modified")
    if last_modified is not None:
        dt: datetime.datetime = parsedate_to_datetime(last_modified)
        return dt.astimezone(datetime.timezone.utc)
    return None


async def get_content_cached_mtime(url: str, *args: Any, **kwargs: Any) -> Tuple[bytes, Optional[datetime.datetime]]:
    """Returns the content of the URL response, and a datetime object for when the content was last modified"""

    # cache the file locally, and store the "last-modified" date as the file mtime
    cache_dir = appconfig.CACHE_DIR
    if cache_dir is None:
        async with httpx.AsyncClient(follow_redirects=True) as client:
            r = await client.get(url, *args, **kwargs)
            return (r.content, get_mtime_for_response(r))

    os.makedirs(cache_dir, exist_ok=True)

    cache_fn = quote_plus(
        (urlparse(url).hostname or "") +
        "." + hashlib.sha256(url.encode()).hexdigest()[:16] +
        ".cache")

    fn = os.path.join(cache_dir, cache_fn)
    if not os.path.exists(fn):
        async with httpx.AsyncClient(follow_redirects=True) as client:
            r = await client.get(url, *args, **kwargs)
            with open(fn, "wb") as h:
                h.write(r.content)
            mtime = get_mtime_for_response(r)
            if mtime is not None:
                os.utime(fn, (mtime.timestamp(), mtime.timestamp()))

    with open(fn, "rb") as h:
        data = h.read()
    file_mtime = datetime.datetime.fromtimestamp(os.path.getmtime(fn), datetime.timezone.utc)
    return (data, file_mtime)


async def get_content_cached(url: str, *args: Any, **kwargs: Any) -> bytes:
    return (await get_content_cached_mtime(url, *args, **kwargs))[0]


def parse_cygwin_versions(base_url: str, data: bytes) -> Dict[str, ExtInfo]:
    # This is kinda hacky: extract the source name from the src tarball and take
    # last version line before it
    version = None
    source_package = None
    versions: Dict[str, ExtInfo] = {}
    base_url = base_url.rsplit("/", 2)[0]
    in_main = True
    for line in data.decode("utf-8").splitlines():
        if line.startswith("@"):
            in_main = True
        if line.startswith("version:"):
            version = line.split(":")[-1].strip().split("-", 1)[0].split("+", 1)[0]
        elif in_main and line.startswith("source:"):
            in_main = False
            source = line.split(":", 1)[-1].strip()
            fn = source.rsplit(None, 2)[0]
            source_package = fn.rsplit("/")[-1].rsplit("-", 3)[0]
            src_url = base_url + "/" + fn
            assert version is not None
            if source_package in versions:
                existing_version = versions[source_package][0]
                if not version_is_newer_than(version, existing_version):
                    continue
            src_url_name = src_url.rsplit("/")[-1]
            versions[source_package] = ExtInfo(
                version, 0,
                "https://cygwin.com/packages/summary/%s-src.html" % source_package,
                {src_url: src_url_name})
    return versions


async def update_cygwin_versions() -> None:
    url = CYGWIN_METADATA_URL
    if not await check_needs_update([url]):
        return
    print("update cygwin info")
    print("Loading %r" % url)
    data = await get_content_cached(url, timeout=REQUEST_TIMEOUT)
    data = zstandard.ZstdDecompressor().decompress(data)
    cygwin_versions = parse_cygwin_versions(url, data)
    state.set_ext_infos(ExtId("cygwin", "Cygwin"), cygwin_versions)


async def update_build_status() -> None:
    urls = BUILD_STATUS_URLS
    if not await check_needs_update(urls):
        return

    print("update build status")
    responses = []
    for url in urls:
        print("Loading %r" % url)
        data, mtime = await get_content_cached_mtime(url, timeout=REQUEST_TIMEOUT)
        print("Done: %r, %r" % (url, str(mtime)))
        responses.append((mtime, url, data))

    # use the newest of all status summaries
    newest = sorted(responses)[-1]
    print("Selected: %r" % (newest[1],))
    state.build_status = BuildStatus.parse_raw(newest[2])


def parse_desc(t: str) -> Dict[str, List[str]]:
    d: Dict[str, List[str]] = {}
    cat = None
    values: List[str] = []
    for l in t.splitlines():
        l = l.strip()
        if cat is None:
            cat = l
        elif not l:
            d[cat] = values
            cat = None
            values = []
        else:
            values.append(l)
    if cat is not None:
        d[cat] = values
    return d


async def parse_repo(repo: Repository) -> Dict[str, Source]:
    sources: Dict[str, Source] = {}
    print("Loading %r" % repo.files_url)

    def add_desc(d: Any) -> None:
        source = Source.from_desc(d, repo)
        if source.name not in sources:
            sources[source.name] = source
        else:
            source = sources[source.name]

        source.add_desc(d, repo)

    data = await get_content_cached(repo.files_url, timeout=REQUEST_TIMEOUT)

    with io.BytesIO(data) as f:
        with ExtTarFile.open(fileobj=f, mode="r") as tar:
            packages: Dict[str, list] = {}
            for info in tar:
                package_name = info.name.split("/", 1)[0]
                infofile = tar.extractfile(info)
                if infofile is None:
                    continue
                with infofile:
                    packages.setdefault(package_name, []).append(
                        (info.name, infofile.read()))

    for package_name, infos in sorted(packages.items()):
        t = ""
        for name, data in sorted(infos):
            if name.endswith("/desc"):
                t += data.decode("utf-8")
            elif name.endswith("/depends"):
                t += data.decode("utf-8")
            elif name.endswith("/files"):
                t += data.decode("utf-8")
        desc = parse_desc(t)
        add_desc(desc)

    return sources


async def update_arch_versions() -> None:
    urls = [i[0] for i in ARCH_REPO_CONFIG]
    if not await check_needs_update(urls):
        return

    print("update versions")
    arch_versions: Dict[str, ExtInfo] = {}
    awaitables = []
    for (url, repo) in ARCH_REPO_CONFIG:
        download_url = url.rsplit("/", 1)[0]
        awaitables.append(parse_repo(Repository(repo, "", "", "", download_url, download_url, "")))

    # priority: real packages > real provides > aur packages > aur provides

    for sources in (await asyncio.gather(*awaitables)):
        for source in sources.values():
            version = extract_upstream_version(arch_version_to_msys(source.version))
            for p in source.packages.values():
                url = "https://archlinux.org/packages/%s/%s/%s/" % (
                    p.repo, p.arch, p.name)

                if p.name in arch_versions:
                    old_ver = arch_versions[p.name][0]
                    if version_is_newer_than(version, old_ver):
                        arch_versions[p.name] = ExtInfo(version, p.builddate, url, {})
                else:
                    arch_versions[p.name] = ExtInfo(version, p.builddate, url, {})

            url = "https://archlinux.org/packages/%s/%s/%s/" % (
                source.repos[0], source.arches[0], source.name)
            if source.name in arch_versions:
                old_ver = arch_versions[source.name][0]
                if version_is_newer_than(version, old_ver):
                    arch_versions[source.name] = ExtInfo(version, source.date, url, {})
            else:
                arch_versions[source.name] = ExtInfo(version, source.date, url, {})

            # use provides as fallback
            for p in source.packages.values():
                url = "https://archlinux.org/packages/%s/%s/%s/" % (
                    p.repo, p.arch, p.name)

                for provides in sorted(p.provides.keys()):
                    if provides not in arch_versions:
                        arch_versions[provides] = ExtInfo(version, p.builddate, url, {})

    print("done")
    state.set_ext_infos(ExtId("archlinux", "Arch Linux"), arch_versions)

    print("update versions from AUR")
    aur_versions: Dict[str, ExtInfo] = {}
    r = await get_content_cached(AUR_METADATA_URL,
                                 timeout=REQUEST_TIMEOUT)
    items = json.loads(r)
    for item in items:
        name = item["Name"]
        # We use AUR as a fallback only, since it might contain development builds
        if name in arch_versions:
            continue
        version = item["Version"]
        msys_ver = extract_upstream_version(arch_version_to_msys(version))
        last_modified = item["LastModified"]
        url = "https://aur.archlinux.org/packages/%s" % name
        aur_versions[name] = ExtInfo(msys_ver, last_modified, url, {})

    for item in items:
        name = item["Name"]
        for provides in sorted(item.get("Provides", [])):
            if provides in arch_versions:
                continue
            version = item["Version"]
            msys_ver = extract_upstream_version(arch_version_to_msys(version))
            last_modified = item["LastModified"]
            url = "https://aur.archlinux.org/packages/%s" % name
            aur_versions[provides] = ExtInfo(msys_ver, last_modified, url, {})

    print("done")
    state.set_ext_infos(ExtId("aur", "AUR"), aur_versions)


async def check_needs_update(urls: List[str], _cache: Dict[str, str] = {}) -> bool:
    """Raises RequestException"""

    if appconfig.CACHE_DIR:
        return True

    async def get_headers(client: httpx.AsyncClient, url: str, *args: Any, **kwargs: Any) -> Tuple[str, httpx.Headers]:
        r = await client.head(url, *args, **kwargs)
        r.raise_for_status()
        return (url, r.headers)

    needs_update = False
    async with httpx.AsyncClient(follow_redirects=True) as client:
        awaitables = []
        for url in urls:
            awaitables.append(get_headers(client, url, timeout=REQUEST_TIMEOUT))

        for url, headers in (await asyncio.gather(*awaitables)):
            old = _cache.get(url)
            new = headers.get("last-modified", "")
            new += headers.get("etag", "")
            if old != new:
                needs_update = True
            _cache[url] = new

    return needs_update


async def update_source() -> None:
    """Raises RequestException"""

    urls = [repo.files_url for repo in get_repositories()]
    if not await check_needs_update(urls):
        return

    print("update source")

    final: Dict[str, Source] = {}
    awaitables = []
    for repo in get_repositories():
        awaitables.append(parse_repo(repo))
    for sources in await asyncio.gather(*awaitables):
        for name, source in sources.items():
            if name in final:
                final[name].packages.update(source.packages)
            else:
                final[name] = source

    fill_rdepends(final)
    fill_provided_by(final)
    state.sources = final


async def update_sourceinfos() -> None:
    urls = SRCINFO_URLS
    if not await check_needs_update(urls):
        return

    print("update sourceinfos")
    result: Dict[str, SrcInfoPackage] = {}

    for url in urls:
        print("Loading %r" % url)
        data = await get_content_cached(url, timeout=REQUEST_TIMEOUT)
        json_obj = json.loads(gzip.decompress(data).decode("utf-8"))
        for hash_, m in json_obj.items():
            for repo, srcinfo in m["srcinfo"].items():
                for pkg in SrcInfoPackage.for_srcinfo(srcinfo, repo, m["repo"], m["path"], m["date"]):
                    if pkg.pkgname in result:
                        print(f"WARN: duplicate: {pkg.pkgname} provided by "
                              f"{pkg.pkgbase} and {result[pkg.pkgname].pkgbase}")
                    result[pkg.pkgname] = pkg

    state.sourceinfos = result


async def update_pkgmeta() -> None:
    urls = PKGMETA_URLS
    if not await check_needs_update(urls):
        return

    print("update pkgmeta")
    merged = PkgMeta(packages={})
    for url in urls:
        print("Loading %r" % url)
        data = await get_content_cached(url, timeout=REQUEST_TIMEOUT)
        merged.packages.update(PkgMeta.parse_obj(yaml.safe_load(data)).packages)

    state.pkgmeta = merged


def fill_rdepends(sources: Dict[str, Source]) -> None:
    deps: Dict[str, Dict[Package, Set[DepType]]] = {}
    for s in sources.values():
        for p in s.packages.values():
            for n, r in p.depends.items():
                deps.setdefault(n, dict()).setdefault(p, set()).add(DepType.NORMAL)
            for n, r in p.makedepends.items():
                deps.setdefault(n, dict()).setdefault(p, set()).add(DepType.MAKE)
            for n, r in p.optdepends.items():
                deps.setdefault(n, dict()).setdefault(p, set()).add(DepType.OPTIONAL)
            for n, r in p.checkdepends.items():
                deps.setdefault(n, dict()).setdefault(p, set()).add(DepType.CHECK)

    for s in sources.values():
        for p in s.packages.values():
            rdeps = [deps.get(p.name, dict())]
            for prov in p.provides:
                rdeps.append(deps.get(prov, dict()))

            merged: Dict[Package, Set[DepType]] = {}
            for rd in rdeps:
                for rp, rs in rd.items():
                    merged.setdefault(rp, set()).update(rs)

            p.rdepends = merged


def fill_provided_by(sources: Dict[str, Source]) -> None:

    provided_by: Dict[str, Set[Package]] = {}
    for s in sources.values():
        for p in s.packages.values():
            for provides in p.provides.keys():
                provided_by.setdefault(provides, set()).add(p)
    for s in sources.values():
        for p in s.packages.values():
            if p.name in provided_by:
                p.provided_by = provided_by[p.name]


_rate_limit = AsyncLimiter(UPDATE_MIN_RATE, UPDATE_MIN_INTERVAL)


@functools.lru_cache(maxsize=None)
def _get_update_event() -> Event:
    return Event()


async def wait_for_update() -> None:
    update_event = _get_update_event()
    await update_event.wait()
    update_event.clear()


def queue_update() -> None:
    update_event = _get_update_event()
    update_event.set()


async def trigger_loop() -> None:
    while True:
        print("Sleeping for %d" % UPDATE_INTERVAL)
        await asyncio.sleep(UPDATE_INTERVAL)
        queue_update()


async def update_loop() -> None:
    asyncio.create_task(trigger_loop())
    while True:
        async with _rate_limit:
            print("check for updates")
            try:
                awaitables = [
                    update_pkgmeta(),
                    update_cygwin_versions(),
                    update_arch_versions(),
                    update_source(),
                    update_sourceinfos(),
                    update_build_status(),
                ]
                await asyncio.gather(*awaitables)
                state.ready = True
                print("done")
            except Exception:
                traceback.print_exc(file=sys.stdout)
        print("Waiting for next update")
        await wait_for_update()
        # XXX: it seems some updates don't propagate right away, so wait a bit
        await asyncio.sleep(5)